I rented from Avis and used Amex and was covered. I was also familiar with the Ireland roads so rented the smallest car available. When I got there they had upgraded me two levels to a much bigger car. I asked for what I reserved and it was not available. So I had a big car, standard shift right hand steering. Lots of fun. I am very used to driving from the right, but shifting from the right is a bit of a challenge. And yes the roads are very narrow.

Another rental car strange Ireland common issue is that for the week from Avis my rental car was like 85 euros. Get an automatic and it went to 380 euros. So learn to drive a stick shift from the right hand drive.